DM Dysfunction Research Articles

In utero exposure to maternal diabetes exacerbates dietary sodium intake-induced endothelial dysfunction by activating cyclooxygenase 2-derived prostanoids.

Prenatal exposure to maternal diabetes has been recognized as a significant cardiovascular risk factor, increasing the susceptibility to the emergence of conditions such as high blood pressure, atherosclerosis, and heart disease in later stages of life. However, it is unclear if offspring exposed to diabetes in utero have worse vascular outcomes on a high-salt (HS) diet. To test the hypothesis that in utero exposure to maternal diabetes predisposes to HS-induced vascular dysfunction, we treated adult male wild-type offspring (DM_Exp, 6 mo old) of diabetic Ins2+/C96Y mice (Akita mice) with HS (8% sodium chloride, 10 days) and analyzed endothelial function via wire myograph and cyclooxygenase (COX)-derived prostanoids pathway by ELISA, quantitative PCR, and immunochemistry. On a regular diet, DM_Exp mice did not manifest any vascular dysfunction, remodeling, or inflammation. However, HS increased aortic contractility to phenylephrine and induced endothelial dysfunction (analyzed by acetylcholine-induced endothelium-dependent relaxation), vascular hydrogen peroxide production, COX2 expression, and prostaglandin E2 (PGE2) overproduction. Interestingly, ex vivo antioxidant treatment (tempol) or COX1/2 (indomethacin) or COX2 (NS398) inhibitors improved or reverted the endothelial dysfunction in DM_Exp mice fed a HS diet. Finally, DM_Exp mice fed with HS exhibited greater circulating cytokines and chemokines accompanied by vascular inflammation. In summary, our findings indicate that prenatal exposure to maternal diabetes predisposes to HS-induced vascular dysfunction, primarily through the induction of oxidative stress and the generation of COX2-derived PGE2. This supports the concept that in utero exposure to maternal diabetes is a cardiovascular risk factor in adulthood.NEW & NOTEWORTHY Using a unique mouse model of prenatal exposure to maternal type 1 diabetes, our study demonstrates the novel observation that prenatal exposure to maternal diabetes results in a predisposition to high-salt (HS) dietary-induced vascular dysfunction and inflammation in adulthood. Mechanistically, we demonstrated that in utero exposure to maternal diabetes and HS intake induces vascular oxidative stress, cyclooxygenase-derived prostaglandin E2, and inflammation.

Clinical and Molecular Insights into Gastrointestinal Dysfunction in Myotonic Dystrophy Types 1 & 2.

Myotonic dystrophy (DM) is a highly variable, multisystemic disorder that clinically affects one in 8000 individuals. While research has predominantly focused on the symptoms and pathological mechanisms affecting striated muscle and brain, DM patient surveys have identified a high prevalence for gastrointestinal (GI) symptoms amongst affected individuals. Clinical studies have identified chronic and progressive dysfunction of the esophagus, stomach, liver and gallbladder, small and large intestine, and rectum and anal sphincters. Despite the high incidence of GI dysmotility in DM, little is known regarding the pathological mechanisms leading to GI dysfunction. In this review, we summarize results from clinical and molecular analyses of GI dysfunction in both genetic forms of DM, DM type 1 (DM1) and DM type 2 (DM2). Based on current knowledge of DM primary pathological mechanisms in other affected tissues and GI tissue studies, we suggest that misregulation of alternative splicing in smooth muscle resulting from the dysregulation of RNA binding proteins muscleblind-like and CUGBP-elav-like is likely to contribute to GI dysfunction in DM. We propose that a combinatorial approach using clinical and molecular analysis of DM GI tissues and model organisms that recapitulate DM GI manifestations will provide important insight into defects impacting DM GI motility.

LncRNA H19 inhibits ER stress induced apoptosis and improves diabetic cardiomyopathy by regulating PI3K/AKT/mTOR axis.

Objective: Extensive studies have shown that ERS may be implicated in the pathogenesis of DCM. We explored the therapeutic effects of lncRNAH19 on DCM and its effect on ERS-associated cardiomyocyte apoptosis.Methods: C57/BL-6j mice were randomly divided into 3 groups: non-DM group (controls), DM group (DCM), and lncRNAH19 overexpression group (DCM+H19 group). The effect of H19 on cardiac function was detected. The effect of H19 on cardiomyocyte apoptosis and cardiac fibrosis in DM was examined. Differentially expressed genes (DEGs) and activated pathways were examined by bioinformatics analysis. STRING database was applied to construct a PPI network using Cytoscape software. The expression of p-PERK, p-IRE1, ATF6, CHOP, cleaved caspase-3, -9, -12 and BAX proteins in cardiac tissue was used to determine the ERS-associated apoptotic indicators. We established the HG-stimulated inflammatory cell model. The expression of p-PERK and CHOP in HL-1 cells following HG was determined by immunofluorescence labeling. The effects of H19 on ERS and PI3K/AKT/mTOR pathway were also detected.Results: H19 improved left ventricular dysfunction in DM. H19 could reduce cardiomyocytes apoptosis and improve fibrosis in vivo. H19 could reduce the expression of p-PERK, p-IRE1α, ATF6, CHOP, cleaved caspase-3, cleaved caspase-9, cleaved caspase-12, and BAX proteins in cardiac tissues. Furthermore, H19 repressed oxidative stress, ERS and apoptosis in vitro. Moreover, the effect of H19 on ERS-associated apoptosis might be rescued by LY294002 (the specific inhibitor for PI3K and AKT).Conclusion: H19 attenuates DCM in DM and ROS, ERS-induced cardiomyocyte apoptosis, which is associated with the activation of PI3K/AKT/mTOR signaling pathway.

Angiotensin(1-7) Improves Islet Function in Diabetes Through Reducing JNK/Caspase-3 Signaling.

The aim of this study is to investigate whether Angiotensin (1-7), the physiological antagonist of Angiotensin II (AngII), has antidiabetic activity and the possible mechanism. Male Wistar rats were randomly divided into 3 groups: control group fed the normal diet, DM group fed high-fat diet and injected with STZ, and Angiotensin (1-7) group receiving injection of STZ followed by Angiotensin (1-7) treatment. Serum Ang II, fasting blood glucose, insulin, HOMA-IR, and HOMA-beta were determined in control, diabetes and Angiotensin (1-7) groups. The increased AngII and insulin resistance in diabetes group were accompanied by changes in islet histopathology. However, Angiotensin (1-7) improved the islet function and histopathology in diabetes without affecting the level of AngII. Western blot confirmed that Angiotensin (1-7) decreased the cleaved caspase 3 levels in pancreas of DM. The increased expression of JNK, Bax, and Bcl2 genes under diabetic conditions were partially reversed after Angiotensin (1-7) administration in pancreas. Immunofluorescence analysis showed that p-JNK was markedly increased in islet of DM rats, which was markedly alleviated after Angiotensin (1-7) treatment. Furthermore, Angiotensin (1-7) reversed high glucose(HG) induced mitochondrial apoptosis augments. Finally, Angiotensin (1-7) attenuated the apoptosis of INS-1 cells through reducing JNK activation in diabetes, which was blocked by anisomycin (a potent agonist of JNK). Our findings provide supporting evidence that Angiotensin (1-7) improved the islet beta-cells apoptosis by JNK-mediated mitochondrial dysfunction, which might be a novel target for the treatment and prevention of beta-cells dysfunction in DM.

Endothelial dysfunction caused by circulating microparticles from diabetic mice is reduced by PD98059 through ERK and ICAM-1

Endothelial dysfunction contributes to the development of diabetic complications and the production of circulating microparticles (MPs). Our previous study showed that diabetic mice-derived MPs (DM MPs) had increased levels of extracellular regulated protein kinase 1/2 (ERK1/2) and impaired endothelial-dependent relaxation in aortas when compared with control mice-derived MPs. This study was designed to investigate whether PD98059, an ERK1/2 inhibitor, affects the function of aortas and DM MPs. MPs were obtained from streptozotocin-induced DM, DM after PD98059 treatment, and ICR mice as control. The mice and MPs were then analyzed on the basis of their vascular function and enzyme expressions. Compared with the controls, platelet-derived MPs and ERK1/2 levels in the MPs were significantly elevated in the DM but showed little change in PD98059-treated DM. PD98059 mainly decreased ERK1/2 phosphorylation in the MPs. In the aortas of DM and DM MPs the endothelium-dependent vascular function was impaired, and there was a significantly greater improvement in the vascular function in the PD98059-treated DM aortas and the aortas treated with PD98059-treated DM MPs than in DM aortas and the aortas treated with DM MPs. Furthermore, DM MPs increased ERK1/2 and intracellular adhesion molecule-1 (ICAM-1) expressions in the aortas, but PD98059-treated DM MPs did not show these effects. For the first time, these results indicate that PD98059 treatment improves endothelial dysfunction in DM, and adhesion properties of DM MPs can be partly blocked by PD98059 via ERK and ICAM-1. These effects may explain some of the vascular complications in diabetes.

The human type 2 diabetes-specific visceral adipose tissue proteome and transcriptome in obesity

Dysfunctional visceral adipose tissue (VAT) in obesity is associated with type 2 diabetes (DM) but underlying mechanisms remain unclear. Our objective in this discovery analysis was to identify genes and proteins regulated by DM to elucidate aberrant cellular metabolic and signaling mediators. We performed label-free proteomics and RNA-sequencing analysis of VAT from female bariatric surgery subjects with DM and without DM (NDM). We quantified 1965 protein groups, 23 proteins, and 372 genes that were differently abundant in DM vs. NDM VAT. Proteins downregulated in DM were related to fatty acid synthesis and mitochondrial function (fatty acid synthase, FASN; dihydrolipoyl dehydrogenase, mitochondrial, E3 component, DLD; succinate dehydrogenase-α, SDHA) while proteins upregulated in DM were associated with innate immunity and transcriptional regulation (vitronectin, VTN; endothelial protein C receptor, EPCR; signal transducer and activator of transcription 5B, STAT5B). Transcriptome indicated defects in innate inflammation, lipid metabolism, and extracellular matrix (ECM) function, and components of complement classical and alternative cascades. The VAT proteome and transcriptome shared 13 biological processes impacted by DM, related to complement activation, cell proliferation and migration, ECM organization, lipid metabolism, and gluconeogenesis. Our data revealed a marked effect of DM in downregulating FASN. We also demonstrate enrichment of complement factor B (CFB), coagulation factor XIII A chain (F13A1), thrombospondin 1 (THBS1), and integrins at mRNA and protein levels, albeit with lower q-values and lack of Western blot or PCR confirmation. Our findings suggest putative mechanisms of VAT dysfunction in DM.

1973-P: Single-Nuclei Transcriptomics of Human Adipose Tissue Identify Distinct Adipocyte Progenitor Subpopulations in Type 2 Diabetes

Altered adipocyte function underlies type 2 diabetes (DM) pathogenesis. We hypothesized that adipocyte dysfunction in visceral adipose tissue (VAT) in DM originates from distinct adipocyte progenitor cell (APC) subpopulations. VAT was collected from bariatric surgery patients with (HbA1c>6.5) and without DM (NDM, HbA1c<5.7). Single-nuclei RNA sequencing was performed in VAT nuclei (n= 1 NDM, 2 DM) using 10X Genomics. Transcriptionally distinct cell subpopulations were identified by DEG: mature adipocytes (ADIPOQ, LEP), endothelial cells (VWR), immune cells (F13A1, MSR1), and two major APC subpopulations (S1: FABP4, ADIRF, ITLN1 and MSLN; S2: APOD, CFD and WISP2). S2 was uniquely identified by the upregulation of extracellular matrix accumulation and fibrosis markers: LUM, DCN, FBN1, and COL1A1, 3A1, 6A1 and 6A3. S2 had higher expression of APC and committed preadipocyte markers, such as PLIN1, GNAI1, CXCL14, CP, and CRISPLD2, while S1 had higher mesothelial-like cell markers GPM6A, PKHD1L1, LRRN4, CXADR, SLPI, and UPK3B. We FACS-isolated S1 and S2 from VAT CD31-CD45- cells (n= 3 NDM, 5 DM) using the surface marker TM4SF1, which was abundantly expressed in S1, but not S2. TM4SF1 expression (qPCR) was 50% higher in S1 (TM4SF1+) than in S2 (TM4SF1-). TM4SF1 immunostaining of human SVF confirmed distinct APC subpopulations. S1 corresponded to 15 ± 3% and S2 to 69 ± 2% of CD31-CD45- cells. In DM compared to NDM, S2 fraction was increased by 12% while S1 was decreased by 45%. We tested the metabolic function of S1 and S2 sorted from 5 DM VAT. Both subpopulations differentiated into lipid-filled adipocytes upon adipogenic induction in vitro. However, S2 compared to S1, manifested decreased proliferation and increased intracellular lipid accumulation and lipolytic response, consistent with a pro-hypertrophic, lipolytic adipocyte phenotype in DM. Our data suggest that distinct APC subpopulations in human obese VAT contribute to adipose tissue dysfunction in DM. Disclosure C. Strieder-Barboza: None. C.G. Flesher: None. L.M. Geletka: None. R.W. ORourke: None. C.N. Lumeng: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases (R01DK115190, DK090262)

Impact of cigarette smoking on kidney inflammation and fibrosis in diabetic rats

Background: Cigarette smoking is a very common habit worldwide contributing to risk of kidney dysfunction and diabetes (DM). However, the mechanisms are unclear.Aim: The goal of the present study was to assess the effects of cigarette smoking on kidney oxidative stress, inflammation, and remodeling in streptozotocin (STZ) rat model of diabetes.Methods: Rats were randomized into control (intraperitoneal (i.p.) citrate buffer injection and exposure to fresh air), cigarette smoking (1 h daily for 6 d/week, citrate buffer), DM (single dose STZ 35 mg/kg i.p. and exposure to fresh air), and DM + smoking groups for a period of 4 weeks. Kidney biomarkers of inflammation, oxidative stress, and remodeling were measured.Results: A significant increase in kidney to body weight ratio was observed in diabetic groups. Diabetes but not smoking increased blood urea nitrogen levels without changes in creatinine levels. Kidney levels of thiobarbituric acid substances, nitrite, endothelin-1, and C-reactive protein were increased significantly in the DM + smoking groups. Smoking induced GSH expression and activity of superoxide dismutase. A significant increase in kidney fibrosis was observed in the DM + smoking group coupled with a similar increase in transforming growth factor beta. Protein levels of matrix metalloproteinase-2, (MMP-2), mitogen-activated protein kinases, and c-Jun N terminal kinase were elevated in Smoking and DM + smoking groups.Conclusion: Cigarette smoke might promote risk of kidney dysfunction in DM by augmentation of renal inflammation, oxidant radicals and fibrosis. The kidney promotes compensatory increase in MMP-2 in response to smoking probably to prevent pro-fibrotic factors induced-fibrosis.

Modeling of Myotonic Dystrophy Cardiac Phenotypes in Drosophila.

After respiratory distress, cardiac dysfunction is the second most common cause of fatality associated with the myotonic dystrophy (DM) disease. Despite the prevalance of heart failure in DM, physiopathological studies on heart symptoms have been relatively scarce because few murine models faithfully reproduce the cardiac disease. Consequently, only a small number of candidate compounds have been evaluated in this specific phenotype. To help cover this gap Drosophila combines the amenability of its invertebrate genetics with the possibility of quickly acquiring physiological parameters suitable for meaningful comparisons with vertebrate animal models and humans. Here we review available descriptions of cardiac disease in DM type 1 and type 2, and three recent papers reporting the cardiac toxicity of non-coding CUG (DM1) and CCUG (DM2) repeat RNA in flies. Notably, flies expressing CUG or CCUG RNA in their hearts developed strong arrhythmias and had reduced fractional shortening, which correlates with similar phenotypes in DM patients. Overexpression of Muscleblind, which is abnormally sequestered by CUG and CCUG repeat RNA, managed to strongly suppress arrhythmias and fractional shortening, thus demonstrating that Muscleblind depletion causes cardiac phenotypes in flies. Importantly, small molecules pentamidine and daunorubicin were able to rescue cardiac phenotypes by releasing Muscleblind from sequestration. Taken together, fly heart models have the potential to make important contributions to the understanding of the molecular causes of cardiac dysfunction in DM and in the quick assessment of candidate therapeutics.

Social Cognitive Impairment in Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM 1) is a heritable, multisystem disease that affects not only the muscles but also the brain. DM 1 is often accompanied by developmental behavioral disorders, such as autism spectrum disorders. The autistic traits in DM 1 may be related to social cognitive dysfunction. The social cognitive function of patients with DM 1 was examined with respect to facial emotion recognition and theory of mind, which is the specific cognitive ability to understand the mental states of other people. With respect to facial emotion recognition, the sensitivities to disgust and anger were lower among patients with DM 1 than among healthy subjects, and this difference could not be attributed to visual impairment. To examine the theory of mind ability, the "Reading the Mind in the Eyes" test and the faux pas recognition test were used. Patients with DM 1 were found to be impaired in both tests, but the results were not attributed to visual ability and lexical comprehension. The possible causes of social cognitive dysfunction in DM 1 are the l cerebral atrophy and white matter abnormalities in the temporal, frontal, and insular cortex. Dysfunctions in these areas may affect the emotional and theory of mind abilities in DM 1, which result in the behavioral and communication disorders.

Epigenetic Mechanisms of Endothelial Progenitor Cell Dysfunction

Diabetes mellitus remains a leading factor contributing increased morbidity and mortality worldwide. The development and progression of DM associates with microvascular and macrovascular complications linked the DM with cardiovascular events. The impaired ability of endothelium to repair the injury and restore integrity depends in part on number and function of endothelial progenitor cells (EPCs). The mechanisms underlying EPC dysfunction in DM predominantly include weak bone marrow mobilization, decreased proliferation, and shortened survival. The weak function and lowered number of EPCs obtained from peripheral blood were recently found in 1 type and 2 type of DM. It has suggested that glucose toxicity, lipid toxicity, inflammation and oxidative stress may directly and indirectly via several molecular mechanisms worse of EPCs function and, however, lead to deficiency of circulating angiopoetic progenitors. Epigenetic changes are considered important key to understand whether EPCs dysfunction is reversible setting or not. The aim of editorial is to discuss around the role of epigenetic changes in EPCs in linking of DM with cardiovascular risk.

Benzodiazepine & nonbenzodiazepine prescriptions for Taiwanese elderly with type 2 diabetes contributes to cognitive dysfunction.

This study examined the relationship of cognitive function and benzodiazepine/nonbenzodiazepine hypnotics (BZD/nonBZD) and other risk factors in a national sample of Taiwan's elderly diabetic patients. Data were drawn from the "2005 Taiwan National Health Interview Survey (NHIS)", a population-based study of a national sample of adults aged 65 years and older. A total of 653 participants were included in this study. The Mini-Mental State Examination (MMSE) was used to evaluate patient's cognitive function for which the cut-off score is education-adjusted. There were 130 participants left in the diabetic group and 523 participants in the control group. The average age was 74.2 and 73.3 respectively. The rate of cognitive dysfunction in DM and non DM participants was 11.5% (15/130) and 8.4% (44/523). Compared with those without diabetes in multivariate logistic regression, the odds ratio of cognitive impairment was 1.87-fold higher for diabetic patients (95% CI 1.04-3.61) after adjusting for sociodemographic characteristics, comorbidities, and BZD/nonBZD. Other factors were not significant. We performed an additional logistic analysis for which the odds ratio of cognitive impairment in diabetic patients with BZD/nonBZD was significantly increased to 2.41 (95% CI 1.08-5.40) than for patients without diabetes and BZD/nonBZD. In our research, cognitive dysfunction was associated with diabetes. BZD/nonBZD may have conferred additional risk of cognitive impairment in our elderly diabetic patients. We should consider examining the mental function of DM patients regularly and try our best to avoid potentially inappropriate medications (PIMs).

Relationship between proinsulin and beta cell function in different states of glucose tolerance

To measure proinsulin concentrations in different states of glucose tolerance and examine the relationship between proinsulin and beta cell function. Serum true insulin (TI), proinsulin (PI), immunoreactive insulin (IRI), C peptide (CP) and blood glucose (BG) levels were measured in the fasting state and during an oral glucose tolerance test (OGTT) in 32 individuals with normal glucose tolerance (NGT), 42 individuals with impaired glucose tolerance (IGT), and 54 individuals with newly diagnosed type 2 diabetes mellitus. All participants were also subdivided into nonobese [body mass index (BMI) <25 kg/m2] and obese (BMI ≥25 kg/m2) subgroups. The levels of TI, PI, IRI and CP were higher in obese patients compared with the corresponding NGT subgroup, whereas there was no difference in PI/TI. The levels of IRI, PI and PI/TI were higher in nonobese patients with type 2 diabetes mellitus than in the corresponding NGT subgroup. The levels of PI and TI increased in obese patients with NGT and IGT, whereas PI/TI did not change. In contrast, PI increased but TI did not in subjects with newly diagnosed diabetes mellitus, which led to an increase in PI/TI, and a decrease in beta cell function. Therefore, PI and the PI/TI ratio could offer markers for beta cell dysfunction in DM.

Age is a determinant of acute hemodynamic responses to hyperglycemia and angiotensin II in humans with uncomplicated type 1 diabetes mellitus

Hyperglycemia is associated with hemodynamic changes in type 1 diabetes (DM), acting in part through renin-angiotensin system activation. Since aging is associated with vascular dysfunction in DM, we hypothesized that acute hemodynamic responses to clamped hyperglycemia and infused ANG II would be exaggerated in older adults compared with a group of adolescent/young adults with type 1 DM. Renal hemodynamic function, blood pressure, and arterial stiffness were assessed in adolescent/young adults (n = 34; mean age: 18 +/- 3 yr) and older adults (n = 32; mean age: 45 +/- 9 yr). Studies were performed during clamped euglycemia (4-6 mmol/l) and hyperglycemia (9-11 mmol/l). Renal and systemic hemodynamic responses to ANG II were measured during clamped euglycemia in diabetic subjects. ANG II responses were also assessed in a cohort of non-DM subjects (n = 97; mean age: 26; age range: 18-40 yr). Older DM adults exhibited higher baseline blood pressure, arterial stiffness, and renal vascular resistance, and lower glomerular filtration rate (GFR) and effective renal plasma flow, compared with adolescent/young DM adults (P < 0.05). Clamped hyperglycemia was associated with exaggerated peripheral and renal hemodynamic responses uniquely in older DM adults; only GFR increased in adolescent/young DM adults. ANG II infusion also produced exaggerated vasoconstrictive responses in older DM adults vs. adolescent/young DM adults (P < 0.05). The independent effect of age on hemodynamic responses to hyperglycemia and ANG II was confirmed using multivariate regression analysis in DM subjects (P < 0.05), and results were still significant when participants were matched for DM duration. Age-related alterations in hemodynamic function and ANG II response were not observed in healthy non-DM control subjects. Acute hemodynamic responses to clamped hyperglycemia and ANG II were exaggerated in older subjects with type 1 DM, highlighting an important interaction between age and factors that contribute to the pathogenesis of acute vascular dysfunction in DM.

Abstract 5515: Mitochondrial Membrane Hyperpolarization and Reduced Mitochondrial Mass Characterize the Arteriolar Endothelium and Mononuclear Cells of Humans With Type 2 Diabetes Mellitus- in vivo and in vitro Assessment of Endothelial Function

Background: Endothelial dysfunction and inflammation are central to the vascular pathology of Type 2 diabetes (DM). In vitro data suggest excessive mitochondrial reactive oxygen species production contributes to endothelial dysfunction in part due to pathological hyperpolarization of mitochondrial membrane potential (ΔΨ m ). ΔΨ m hyperpolarization in leukocytes is also associated with activation of the inflammatory response. Mitochondrial mass and morphology are also central to mitochondrial function. The relevance of these mechanisms to the human vasculature in DM is unknown. Methods: Blood mononuclear cells were isolated from 30 DM patients and 32 non-diabetics. Subcutaneous arterioles were harvested by gluteal adipose tissue biopsy in a subset (15 DM, 17 controls). ΔΨ m was measured in cells and arterioles using the membrane potential-sensitive fluorescent dye JC-1. Mitochondrial mass was measured using the cardiolipin-specific fluorophore nonyl acridine orange. Endothelium dependent vasodilation was assessed using video microscopy (arterioles) and ultrasonography (brachial artery). Arteriolar vasoreactivity was also determined in the setting of low-dose (100 nM) CCCP to reduce ΔΨ m magnitude. Results: ΔΨ m magnitude of the arteriolar endothelium and mononuclear cells were significantly greater in DM patients [P=0.01 (endothelium), P &lt; 0.0001 (mononuclear cells)]. Mitochondrial mass was significantly lower in DM mononuclear cells (P=0.004), and in DM endothelium following age adjustment (P=0.003). Endothelium dependent vasodilation was impaired in DM in the brachial artery and subcutaneous arterioles (both P&lt;0.001). CCCP treatment of the DM arteriolar endothelium reversed microvascular endothelial dysfunction (P&lt;0.001 vs. untreated). Conclusions: ΔΨ m is hyperpolarized and mitochondrial mass is lower in the arteriolar endothelium and mononuclear cells of DM patients with endothelial dysfunction. Pharmacological normalization of ΔΨ m reverses microvascular endothelial dysfunction in DM. These findings are consistent with experimental studies suggesting a link between mitochondria and vascular disease. Interventions that restore mitochondrial membrane potential and mass in DM may have therapeutic potential.

A role for myotonic dystrophy protein kinase in synaptic plasticity.

Myotonic dystrophy (DM) is associated with an expanded triplet repeat in the 3'-untranslated region of the gene for myotonic dystrophy protein kinase (DMPK), which may reduce DMPK expression. It is unclear how reduced DMPK expression might contribute to the symptoms of DM because the normal function of DMPK is not yet understood. Thus we investigated the function of DMPK to gain insight into how reduced DMPK expression might lead to cognitive dysfunction in DM. We recently demonstrated a role for DMPK in modifying the cytoskeleton, and remodeling of the cytoskeleton is thought to be important for cognitive function. Therefore we hypothesized that DMPK might normally contribute to synaptic plasticity and cognitive function via an effect on actin cytoskeletal rearrangements. To test for involvement of DMPK in synaptic plasticity, we utilized the DMPK null mouse. This mouse showed no changes in baseline synaptic transmission in hippocampal area CA1, nor any changes in long-term synaptic potentiation (LTP) measured 3 h after induction. There was a significant decrease, however, in the decremental potentiation with a duration of 30-180 min that accompanies LTP. These results suggest a role for DMPK in synaptic plasticity that could be relevant to the cognitive dysfunction associated with DM.

Disfunção Endotelial no Diabetes do Tipo 2

A principal etiologia para a mortalidade e grande morbidade dos diabéticos é a ateroesclerose. A hipótese para a lesão inicial da ateroesclerose é a disfunção endotelial, pelo reconhecimento de que o endotélio tem um papel fundamental na manutenção das características de fluidez do sangue, tônus vascular e sua permeabilidade, sendo o óxido nítrico derivado do endotélio (e-NO) o principal protetor contra a moléstia ateroesclerótica por inibir as diversas vias envolvidas na aterogênese. A disfunção endotelial identificada como um marcador precoce de moléstia cardiovascular poderá prever coronariopatia no futuro, mesmo antes que alterações ateroescleróticas evidentes apareçam nas artérias. Assim, medidas da função endotelial poderiam identificar indivíduos com risco para moléstia cardiovascular, como determinar a vaso-dilatação endotélio-dependente pelo fluxo após isquemia induzida, que requer a produção de e-NO. Além disso, pode-se também avaliar a reatividade vascular da microcirculação bem como dosar os marcadores bioquímicos da função endotelial. Finalmente, pode-se fazer a mensuração da espessura da camada médio-intimal de grandes artérias, como as carótidas, um marcador indireto da função do endotélio. A disfunção endotelial tem sido documentada no diabetes (DM), em indivíduos com resistência à insulina ou com alto risco para desenvolver DM do tipo 2, nos quais a hiperglicemia está associada a um aumento do estresse oxidativo, levando a um incremento na formação de radicais oxigênio tais como o superóxido, que reage com o e-NO, levando à sua degradação. No DM do tipo 1 o estado diabético predispõe para a alteração endotelial mas não é suficiente para causá-lo, outros agentes tendo provavelmente um papel. No tipo 2 estão presentes os efeitos do envelhecimento, hipertensão arterial e outros fatores e, em contraste à disfunção no tipo 1, esta pode ser observada anos antes da manifestação da vasculopatia, associada com a resistência à insulina.

Alteration of antioxidants during the progression of heart disease in streptozotocin-induced diabetic rats

Involvement of oxidative stress is implicated in the progression of complication of diabetes mellitus. With respect to heart diseases, we have studied role of oxidative stress/antioxidants using rats treated with streptozotocin to induce diabetes (DM). Hemodynamic and echocardiographic measurements showed thickening of the wall and an increase in the internal dimension of the left ventricle (LV) in DM rats at 8th week. Decrease in diastolic posterior wall velocity and rate of LV pressure change, and increase in LV end diastolic pressures also proved cardiac dysfunction. These changes were further developed in DM rats after 12 weeks. Utilizing rat hearts at 8th and 12th weeks, the following estimations were performed. There was a decrease in the activity of Mn-superoxide dismutase (SOD), suggesting abnormal mitochondrial metabolism of reactive oxygen species. The level of glutathione (GSH) decreased concomitant with a decrease in the expression of γ-glutamylcysteine synthetase (γ-GCS). The expression of transforming growth factor-β1 (TGF-β1), known as a growth factor and a suppressor of GSH synthesis, elevated in DM rat hearts. Immunohistochemical estimation showed an increase in type IV collagen in DM hearts. Collectively, it was suggested a linkage between mitochondrial damage to generate reactive oxygen species and inactivation of Mn-SOD and elevation of the expression of TGF-β1 to lead suppression of GSH synthesis and induction of fibrous change for the consequent cardiac dysfunction in DM.

Skeletal muscle bioenergetics in myotonic dystrophy

Skeletal muscle function of 15 patients with myotonic dystrophy (dystrophia myotonica, DM) was investigated using 31P magnetic resonance spectroscopy to evaluate bioenergetics and intracellular pH at rest and during exercise and recovery. Results from DM patients, normal controls and mitochondrial myopathy patients were compared in order to assess the possible contribution of abnormal mitochondrial metabolism to muscle dysfunction in DM. In resting DM muscle, intracellular pH (pH i) was normal, but there were significant elevations in the concentration ratios of P i ATP , phosphomonoesters/ATP and phosphodiesters/ATP. In patients with the most severe exercise intolerance the phosphocreatine ATP ratio was also reduced. Resting muscle of 11 mitochondrial myopathy patients showed similar changes to those of the most exercise-intolerant DM patients. In exercising DM muscle, energy stores were rapidly depleted as in mitochondrial myopathy. Muscle acidified in all subjects, but in DM the decrease in pH i was less than in normal muscle. Recovery half-times for phosphocreatine, P i and ADP were normal in DM but slow in mitochondrial myopathy. The initial rate of phosphocreatine repletion after exercise was rapid in DM, consistent with high [ADP], but slow in mitochondrial myopathy in spite of elevated [ADP]. Because recovery is an oxidative process, we conclude that there was no decrease in the oxidative capacity of the muscles in this group of DM patients. In the subjects in whom it could be measured, the rate of recovery of intracellular pH was greater in the 3 DM patients (0.14, 0.15 and 0.16 U/min) than in the 7 normal controls (0.08–0.12 U/min, mean 0.10). The results do not rule out a minor abnormality in glycogenolysis, but they suggest that the failure to acidify normally during exercise is probably due to rapid proton efflux.

β-adrenergic system in myotonic dystrophy

Myotonic dystrophy (DM) is considered an inherited membrane disorder, but the basic defect is unknown. We studies plasma catecholamines as well as lymphocyte and muscle β-adrenergic receptor densities and functioning in 19 DM patients and 15 control subjects. Plasma adrenaline and noradrenaline concentrations were not significantly different between DM patients and controls. In isolated lymphocytes basal cAMP production was 157 ± 26 pmol/mg protein/10 min in DM patients and 91 ± 12 pmol/mg protein/10 min in controls (n.s.), whereas isoproterol-stimulated cAMP production was significantly higher in DM patients with (285 ± 42 pmol/mg protein) compared with control subjects (168 ± 21 pmol/mg protein, P < 0.05). Lymphocyte β-adrenoceptor densities were similar among DM patients (50 ± 3 fmol/mg protein) and controls (47 ± 5 fmol/mg protein). β-Adrenoceptor densities were also similar in muscle biopsy specimens (12.9 ± 1 in DM and 13.1 ± 13.1 ± fmol/mg protein in controls). The correlation between lymphocyte and skeletal muscle recert densities was r = 0.35in DM patients and r = 0.22 in controls. The results do not support the hypothesis of adrenergic dysfunction in DM despite its membrane involvement.